1. Field
Embodiments of the invention relate to the field of semiconductor, and more specifically, to lithography.
2. Background
Extreme ultraviolet lithography (EUVL) is a new generation lithography that uses extreme ultraviolet (EUV) radiation with a wavelength in the range of 10 to 14 nanometer (nm) to carry out projection imaging. The EUVL system uses reflective optics and masks in which the image is formed in an absorbing metal.
EUVL masks are patterned from multilayer (ML) mask blanks. To achieve the highest image quality, mask blanks must be manufactured without defects. Due to high degree of accuracy requirements, these ML mask blanks are expensive. Current techniques to fabricate ML mask blanks are for one-time use only. After the mask blank is used for mask patterning, it is usually discarded. Reclaiming the ML blanks with the current design is impossible without sacrificing the quality of the mask.